With IPv6 NAT no longer exists. All your devices are publicly accessible and although they would still be firewalled, in this day and age you need a few layers of protection.
I think this is going to be an interesting problem. I haven't studied it very hard, but I've reviewed some material from someone I know in the IPV6 working group and what you way is essentially correct. The thinking on how home firewalling works is going to have to change because the whole "block by default" paradigm just isn't the same with IPV6's "no NAT" philosophy. But that's way off topic. I just wanted to acknowledge it.
As to X11 being a compatibility problem... well X11 has always required some mucking around to be perfect. I'm not sure what you've experienced, but I haven't had any big issues with it. I don't really use Linux these days, so maybe I shouldn't be commenting... but I do have a VERY long history with Unix and X11. I first customized an X11 window manager in 1991.
I've run X11 on at least 5 flavors of unix (including many versions of Linux) and VNC on 2 or 3 flavors of unix. All without issue. VNC sometimes requires some customization to the startup script, but it's essentially an add on "display" for X, so it mostly just works.
Now, in a perfect world, MC having a web configuration interface would be neat. MC running as a pure daemon would be neat. I absolutely concede those points. But as Hendrik said, it wasn't designed that way from the ground up. MC for Linux is a desktop application that happens to also run on Linux.
Personally, I'm just happy that the best media manager on the planet runs on all three big platforms, and runs well.
Brian.